The present invention relates generally to inventions which are the subject matter of concurrently filed patent application Ser. Nos. 109,653 and 109,892 entitled "Normally Closed Pneumatic Air Valve" and "Electric Air Valve" both of which are assigned to the assignee of the present invention.
The present invention relates to a pneumatic air valve for use in an air distribution system wherein the volume of conditioned air supplied to a zone is varied in order to control the temperature within the zone.
One of the most common types of building ventilation systems is the variable air volume system wherein a central source provides conditioned air which is distributed to various zones within the building via a network of ducts. Since heating and cooling requirements vary from zone to zone, and within individual zones depending upon factors such as solar load and zone usage, it is necessary that provision be made to selectively control the amount of conditioned air supplied to a particular zone in response to local demand.
In a variable air volume system, the selective delivery of conditioned air to a particular zone is accomplished through the provision of at least one air distribution box associated with each zone. Such air distribution boxes define supply plenums and include one or more air outlets in communication with the zone. Additionally, each box has an airflow control valve, for varying the volume of air delivered into the plenum. Such air valves are controlled by a thermostat in the zone so as to supply the proper volume of conditioned air to the zone to maintain or achieve a selected zone temperature.
The present invention is directed to a normally open pneumatic air valve assembly for use in a variable air volume air distribution system.
Typical pneumatically operated air valves are illustrated and described in U.S. Pat. Nos. 4,082,114, to Hantke et al., which is assigned to the assignee of the present invention, and 4,305,418, to Jensen et al. The valve of the Hantke patent includes a closed ended cylindrical portion downstream of the valve inlet in which a generally tubular valve member is disposed for movement axially of the valve housing. The size of a series of radial ports, and therefore the flow of air through the valve, is determined by the position of the valve member within the cylindrical, closed ended valve housing. The valve of the Hantke design is relatively complex and is, as well, somewhat expensive of manufacture. Additionally, dedicated sealing means are required at each peripheral edge of the tubular valve member in order to completely shut off airflow through the valve.
The Jensen valve is a normally closed valve the damper of which is disposed for axial movement interior of a solid, geometrically precise, unitary valve casing. The shape of the valve casing is critical and is selected so as to compensate for the variation of the drag coefficient of the valve. Such variation results from the movement of the damper which is entirely within the valve casing.
The need continues to exist for a normally open pneumatic air valve which is uncomplicated and inexpensive of manufacture yet which provides for the precise control of the volume of air flowing through the valve. The present invention is directed generally to a normally open pneumatic air valve which achieves the precise control of the volume of air flowing therethrough yet which is quiet, relatively inexpensive and extremely reliable.